In general, an ink for writing is divided into a water-based ink and an oil-based ink, and is absorbed or attached to settle onto writing surfaces to maintain a state in which the ink is written for a long period of time. The water-based ink and the oil-based ink for writing are absorbed or attached onto the writing surfaces (for example, a paper, a synthetic resin, etc.), to settle, and are not easily removed.
In a written document employing a writing apparatus using the water-based ink and the oil-based ink for writing, if it happens to require modification of a text or correction of typographical error, the written document needs to be erased, but is not clearly erased with an eraser for general pencil. Further, if it attempts to erase the document with an eraser for a ballpoint pen, a surface settled with the water-based ink and the oil-based ink is ground and ripped off, such that a paper may be torn or deformed.
Accordingly, a technology of manufacturing an ink by using a material having a color-change property in which a colorless compound shows colors, or reversely, a colored compound is changed into colorless by external stimulus, has been recently suggested. The external stimulus may include heat, light, pressure, etc. Particularly, a research into a technology of securing an erasing property of an ink by using a thermochromic compound showing the color-change property in which colorless is implemented from color when applying heat, has been actively conducted.
However, in the thermochromic material in which color-change is performed at a relatively high temperature, there is a limitation in that portability is not satisfied since heating apparatuses such as a hair dryer, hot water, etc., are required to erase the ink.
In addition, in the case of using a material in which thermochromism is possible by body heat, frictional heat due to an eraser, etc., there is a limitation in that a chromogenic property is not sufficiently maintained, for example, color-change is performed even at a summer temperature, etc.
Therefore, development of a thermochromic compound having a color-change temperature range, capable of being rapidly erased by an erasing method with simplicity and portability, while maintaining an excellent chromogenic property has been demanded.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.